This invention relates to a bulk storage facility for the storage of particulate solids which are transported in bulk as an essentially dry powder. This invention is more particularly concerned with a bulk storage facility which is used in combination with one or more conveyor belt systems or the like both to transfer a particulate solid into the facility, and to retrieve a particulate solid from the storage space, or spaces, within the facility.
The name xe2x80x9cCIRC-A-BIN(copyright) STORAGE FACILITYxe2x80x9d will be used for marketing purposes.
Many materials are shipped in bulk as a particulate solid; typical examples are all types of grain, wood chips, coal, alumina and other minerals, sulphur, fertilizers, cement, sand, gravel and crushed stone. These particulate materials range in size from wheat, which is relatively small and has a relatively low bulk density, to minerals, coal and crushed stone which can include particles with a maximum dimension of up to about 20 cm, and which have a considerably higher bulk density. In transporting such materials in bulk, it is commonplace to use more than one form of transport, typically including bulk carrier ships, barges, rail hopper cars and road trucks. These bulk materials are often stored for variable periods of time, particularly when transfer is required to and/or from one form of transport, such as a railcar, to another, such as a bulk carrier ship. In some cases, various types of covered hopper are used for storage, particularly for particulate solids such as grain which need to be protected from weather damage. The particulate solid is usually delivered to the hopper by an overhead conveyor of some sort, ranging from a more or less continuous feed from a conveyor belt, to a crane operated bucket loader. The particulate solid is usually retrieved from the hopper through at least one bottom opening in the hopper, which is closed by at least one discharge gate or basket gate.
In the past, solids such as coal, sundry minerals, sulphur and crushed stone which are more or less resistant to weather damage have been stored in the open in simple heaps, without any protection. This practise is becoming more and more less acceptable for a variety of reasons. First, a particulate solid material can only be readily handled by conveyor systems when it is free flowing: storage in the open can result in a wet material which does not flow readily. Second, when handled in a reasonably dry state many of these solids present pollution problems, ranging from the consequences of associated dust, for example, coal dust which will coat any more or less horizontal surface, to the dispersion of potentially toxic air borne dusts into the local environment from many metal ores. Third, when some of these materials are exposed to weathering, potentially toxic contaminants can be leached out of the solids and transferred into the local groundwater.
It can thus be seen that there is a need for a storage facility which can be used as a storage space for materials which are transported in bulk which allows for both storage and retrieval of the material, protects the material from the effects of the weather, and also substantially protects the local environment from pollution derived from, or associated with, the presence of the stored solids. Advantageously, the storage facility should be capable of providing separated storage spaces within which differing products are storable without contamination from other products held in the facility. Additionally, the storage facility should be capable of receiving one product into at least one storage space at the same time as another product is being retrieved from at least one other storage space within the facility.
This invention seeks to provide such a storage facility. In the storage facility of this intention, an arcuate structure is provided which has inner and outer concentric containment walls. The space between the inner and outer walls is subdivided into a plurality of radial storage subspaces, and covered with a continuous roof. A radial stacker conveyor system is provided which receives particulate solids to be stored, and transfers these particulate solids into a selected storage subspace through access apertures disposed on a circular arc in the roof. To allow the radial stacker to access each roof aperture, it is rotatable about an axis concentric with the inner and outer walls, and the roof apertures are located on an arc concentric with the inner and outer walls. A separate radially located conveyor system is provided beneath the floor of each storage subspace, by means of which particulate solid stored in any chosen storage subspace can be retrieved through suitable discharge gates located in the floor of each storage space above the conveyor, and transported to a delivery system adjacent to the radial stacker. The length of arc used for the structure is largely determined by the available space, and the chosen delivery system. Typically the arc length will be about 180xc2x0, and can be 360xc2x0. It can thus be seen that in the arcuate storage facility of this invention particulate solid flows into the storage spaces from the center of the arc, and flows out of the storage subspaces back to the same point. Since the storage subspaces and the conveyor systems can all be enclosed, localised pollution is minimised. Further, since the storage space is protected by a roof, the effects of weather on the stored particulate materials is substantially eliminated.
Thus in a first broad embodiment this invention seeks to provide an arcuate storage facility for a particulate material including in combination:
an arcuate structure having substantially radial end containment walls, inner and outer concentric arcuate containment walls and a floor which in combination define a storage space;
a continuous roof covering the space defined by the end, inner and outer containment walls;
a plurality of access aperture structures in the continuous roof disposed on a circular arc concentric with the inner and outer walls, each of which aperture structures includes a closure means;
a first control means to selectively open and close the access apertures;
a radial stacker means, rotatable about a vertical axis substantially concentric with the inner and outer walls, constructed and arranged to receive a first flow of particulate solids and to transfer the received flow of particulate solids into the facility through a selected aperture in the roof to a first location in the storage space;
a plurality of groups of discharge openings located in the floor, each discharge opening being provided with a discharge gate, and each group of discharge openings being located on a line radial to the inner and outer walls;
a second control means to selectively open and close the discharge gates; and
a plurality of radial conveyor means located beneath the floor, each radial conveyor means being constructed and arranged to receive a second flow of particulate solids from a second selected location within the storage space through at least one open discharge gate, and to transport the received second flow to a location adjacent the axis of the radial stacker, and each conveyor means being located on the same radial line as the group of discharge gates from which it can receive the second flow.
Preferably, the storage space includes internal containment walls providing a plurality of separate subspaces, each subspace including at least one roof access aperture and at least one floor discharge gate. More preferably, the internal containment walls are located radially relative to the inner and outer arcuate walls. Alternatively, the internal walls are arcuate and concentric with the inner and outer walls.
Preferably, the radial stacker means includes a belt conveyor system supported by a support tower and by the inner arcuate wall.
Preferably, the arc length of the arcuate structure is at least about 180xc2x0.